The present disclosure relates to methods of completing wells in subterranean formations, such as in unconsolidated subterranean formations. More particularly, the present disclosure relates to methods of completing wells in unconsolidated subterranean formations for controlling water and particulate production.
Before desirable fluids (e.g., oil, gas, etc.) may be produced from a well bore that has been drilled into a subterranean formation, the well typically must be completed. Well completions may involve a number of stages, including the installation of additional equipment into the well and the performance of procedures to prepare the well for production. By way of example, well completions may include perforating casing that is cemented into the well bore so that fluids can flow, for example, from the formation and into the well bore. Completing the well may also include the installation of production tubing inside the well bore through which fluids may be produced from the bottom of the well bore to the surface. Well completions also may involve a number of other procedures performed in the well and to the surrounding formation, for example, to address issues related to undesired particulate and water production.
Additional procedures also may be needed when wells are completed in certain portions of a subterranean formation, such as in unconsolidated subterranean formations, to prevent undesirable particulate production. As used in this disclosure, the phrase “unconsolidated subterranean formation” refers to a subterranean formation that contains loose particulates and/or particulates bonded with insufficient bond strength to withstand forces created by the production (or injection) of fluids through the formation. These particulates present in the unconsolidated subterranean formation may include, for example, sand, crushed gravel, crushed proppant, fines, and the like. When the well is placed into production, these particulates may migrate out of the formation with the fluids produced by the wells. The presence of such particulates in produced fluids may be undesirable in that the particulates may, for example, abrade downhole and surface equipment (e.g., pumps, flow lines, etc.) and/or reduce the production of desired fluids from the well. By way of example, the migrating particulates may clog flow paths, such as formation pores, perforations, and the like, thereby reducing production.
A number of well completion techniques have been developed to control particulate production in unconsolidated subterranean formations. One technique of controlling particulate production includes placing a filtration bed containing gravel (e.g., a “gravel pack”) near the well bore to provide a physical barrier to the migration of particulates with the production (or injection) of fluids. Typically, such “gravel-packing operations” involve the pumping and placement of a quantity of gravel into the unconsolidated formation in an area adjacent to a well bore. One common type of gravel-packing operation involves placing a screen in the well bore and packing the surrounding annulus between the screen and the well bore with gravel of a specific size designed to prevent the passage of formation sand. The screen is generally a filter assembly used to retain the gravel placed during the gravel-pack operation.
Another technique used to control particulates in unconsolidated formations involves application of a consolidating fluid (e.g., resins, tackifiers, etc.) to consolidate portions of the unconsolidated formation into stable, permeable masses. In general, the consolidating fluid should enhance the grain-to-grain (or grain-to-formation) contact between particulates in the treated portion of the subterranean formation so that the particulates are stabilized, locked in place, or at least partially immobilized such that they are resistant to flowing with produced or injected fluids.
In addition, the undesired production of water may constitute a major expense in the production of hydrocarbons from subterranean formations, for example, due to the energy expended in producing, separating, and disposing of the water. In addition, when produced through unconsolidated subterranean formations, the water may also have an undesirable effect on the migration of formation sands. While wells are typically completed in hydrocarbon-producing formations, a water-bearing zone may occasionally be adjacent to the hydrocarbon-producing formation. In some instances, the water may be communicated with the hydrocarbon-producing formation by way of fractures and/or high-permeability streaks. In addition, undesired water production may be caused by a variety of other occurrences, including, for example, water coning, water cresting, bottom water, channeling at the well bore (e.g., channels behind casing formed by imperfect bonding between cement and casing), and the like.
Accordingly, well completions may include procedures to address issues that may be encountered with the undesired production of water. One attempt to address these issues has been to inject sealing compositions into the formation to form an artificial barrier between the water-bearing zone and the hydrocarbon-producing formation. By way of example, a gelable fluid may be introduced into the formation in a flowable state and thereafter form a gel in the formation that plugs off formation flow paths to eliminate, or at least reduce, the flow of water. Crosslinkable gels have also been used in a similar manner. In addition, certain polymers (commonly referred to as “relative-permeability modifiers”) may be used to reduce the formation's effective permeability to water without a comparable reduction in the formation's effective permeability to hydrocarbons. The use of relative-permeability modifiers may be desirable, for example, where hydrocarbons will be produced from the treated portion of the formation.